Plasma processing apparatus

ABSTRACT

A plasma processing apparatus includes a substrate support having a substrate supporting portion on which a substrate is placed and a peripheral portion surrounding the substrate supporting portion, a conductive focus ring placed on the peripheral portion of the substrate support, a cover ring surrounding an outer periphery of the substrate support and formed of a dielectric material, a conductive ring placed on the cover ring, and a radio frequency power supply electrically coupled to the substrate support. A first surface on an outer peripheral portion of the focus ring and a second surface on an inner peripheral portion of the conductive ring are spaced apart from each other while facing each other. Further, the cover ring has a spacing portion that separates the focus ring from the conductive ring.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application Nos.2019-182194 and 2020-144810, respectively filed on Oct. 2, 2019 and Aug.28, 2020, the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to a plasma processing apparatus.

BACKGROUND

A plasma processing apparatus for performing substrate processing mayinclude a focus ring and a cover ring as disclosed in, e.g., JapanesePatent Application Publication No. 2018-206913. Since a conductive focusring is disposed to surround a periphery of a semiconductor substrate,discontinuity of a bias potential at an edge portion of the substrate issuppressed, and uniformity of plasma processing is improved. A quartzcover ring is disposed around the focus ring (also referred to as “edgering”). An outer peripheral side surface of the focus ring is covered bythe cover ring.

The cover ring made of quartz that covers the outer peripheral sidesurface of the focus ring may be consumed as time elapses due to asputtering of ions of plasma. Since the cover ring is consumedparticularly near the focus ring, the outer peripheral side surface ofthe focus ring covered by the cover ring is exposed to the plasma as thecover ring is consumed. In that case, area variation of the focus ringserving as a cathode occurs. In other words, in a state where the coverring covers the outer peripheral side surface of the focus ring, anupper surface of the focus ring functions as the cathode. In this state,when the cover ring is consumed and the outer peripheral side surface ofthe focus ring is exposed, the outer peripheral side surface of thefocus ring also functions as the cathode. Therefore, process variationsuch as occurrence of tilting at the edge of the substrate may occur dueto the consumption of the cover ring. The present disclosure provides atechnique for suppressing the process variation caused by theconsumption of the cover ring.

SUMMARY

In accordance with an aspect of the present disclosure, there isprovided a plasma processing apparatus including: a substrate supporthaving a substrate supporting portion on which a substrate is placed anda peripheral portion surrounding the substrate supporting portion; aconductive focus ring placed on the peripheral portion of the substratesupport; a cover ring surrounding an outer periphery of the substratesupport and formed of a dielectric material; a conductive ring placed onthe cover ring; and a radio frequency power supply electrically coupledto the substrate support. A first surface on an outer peripheral portionof the focus ring and a second surface on an inner peripheral portion ofthe conductive ring are spaced apart from each other while facing eachother. Further, the cover ring has a spacing portion that separates thefocus ring from the conductive ring.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the present disclosure will become apparentfrom the following description of embodiments, given in conjunction withthe accompanying drawings, in which:

FIG. 1 shows an example of a configuration of a plasma processingapparatus according to an exemplary embodiment;

FIG. 2 shows an example of a structure of a conductive ring according toan exemplary embodiment;

FIG. 3 shows another example of the structure of the conductive ringaccording to the exemplary embodiment.

FIG. 4 shows still another example of the structure of the conductivering according to the exemplary embodiment.

FIG. 5 shows variation of a structure of an inner peripheral bottomsurface of the conductive ring and a structure of a spacing portion;

FIG. 6 shows further still another example of the structure of theconductive ring according to the exemplary embodiment;

FIG. 7 shows further still another example of the structure of theconductive ring according to the exemplary embodiment; and

FIG. 8 shows further still another example of the structure of theconductive ring according to the exemplary embodiment.

DETAILED DESCRIPTION

Hereinafter, various exemplary embodiments will be described.

In one exemplary embodiment, a plasma processing apparatus is provided.The plasma processing apparatus includes a substrate support, aconductive focus ring, a cover ring, a conductive ring, and a radiofrequency power supply. The substrate support has a substrate supportingportion on which a substrate is placed and a peripheral portionsurrounding the substrate supporting portion. The conductive focus ringis placed on the peripheral portion of the substrate support. The coverring surrounds an outer periphery of the substrate support and is formedof a dielectric material. The conductive ring is placed on the coverring. The radio frequency power supply is electrically coupled to thesubstrate support. A first surface on an outer peripheral portion of thefocus ring and a second surface on an inner peripheral portion of theconductive ring are spaced apart from each other while facing eachother. The cover ring has a spacing portion that separates the focusring from the conductive ring. A first side surface of an outerperiphery of the focus ring and a second side surface of an innerperiphery of the conductive ring are spaced apart from each other whilefacing each other. The focus ring functions as a cathode during plasmaprocessing. The conductive ring in an electrically floating state isdisposed to face the outer periphery of the focus ring.

In one exemplary embodiment, an inner peripheral portion of the focusring may be supported on the peripheral portion of the substratesupport, and the outer peripheral portion of the focus ring may cover anupper surface of an inner peripheral portion of the cover ring.

In one exemplary embodiment, the first surface may be a side surface ofthe outer peripheral portion of the focus ring, and the second surfacemay be a side surface of the inner peripheral portion of the conductivering.

In one exemplary embodiment, the first surface may be a bottom surfaceof the outer peripheral portion of the focus ring, and the secondsurface may be an upper surface of the inner peripheral portion of theconductive ring.

In one exemplary embodiment, the first surface may be an upper surfaceof the outer peripheral portion of the focus ring, and the secondsurface may be a bottom surface of the inner peripheral portion of theconductive ring. In one exemplary embodiment, a side surface of theouter peripheral portion of the focus ring and a side surface of theinner peripheral portion of the conductive ring may be spaced apart fromeach other while facing each other.

In one exemplary embodiment, an area of the upper surface of the innerperipheral portion of the conductive ring facing the bottom surface ofthe outer peripheral portion of the focus ring may be greater than anarea of the side surface of the inner peripheral portion of theconductive ring facing the side surface of the outer peripheral portionof the focus ring.

In one exemplary embodiment, a gap between the bottom surface of theouter peripheral portion of the focus ring and the upper surface of theinner peripheral portion of the conductive ring may be smaller than agap between the side surface of the outer peripheral portion of thefocus ring and the side surface of the inner peripheral portion of theconductive ring.

In one exemplary embodiment, the focus ring and the conductive ring maybe capacitively coupled between the first surface and the secondsurface.

In one exemplary embodiment, a distance between the first surface andthe second surface may be greater than zero and smaller than a thicknessof the focus ring.

In one exemplary embodiment, a bottom surface of the inner peripheralportion of the conductive ring may be lower than a bottom surface of theouter peripheral portion of the focus ring.

In one exemplary embodiment, the spacing portion may be a groove portionformed on a surface of the cover ring, and a bottom surface of the innerperipheral portion of the conductive ring may be fitted in the grooveportion.

In one exemplary embodiment, the spacing portion may be a steppedportion formed on a surface of the cover ring that is in contact with aside surface of the inner peripheral portion of the conductive ring.

In one exemplary embodiment, the conductive ring may be disposed on thecover ring such that an outer periphery of the conductive ring islocated on an inner side compared to an outer periphery of the coverring, and an upper surface of an outer peripheral portion of the coverring may be exposed to a plasma processing space.

In one exemplary embodiment, the cover ring may include a plurality ofdielectric parts.

In one exemplary embodiment, the substrate supporting portion and theperipheral portion may serve as an electrostatic chuck.

In one exemplary embodiment, the substrate supporting portion may serveas an electrostatic chuck, and the peripheral portion may serve as abase of the substrate support.

In one exemplary embodiment, the conductive ring may have a slopedportion between an upper surface of the conductive ring and a sidesurface of the inner peripheral portion of the conductive ring.

In one exemplary embodiment, the conductive ring may be formed ofsilicon or silicon carbide, and the cover ring may be formed of quartz.

Hereinafter, embodiments will be described in detail with reference tothe accompanying drawings. Like reference numerals will be given to likeor corresponding parts throughout the drawings.

The plasma processing apparatus 1 according to an exemplary embodimentincludes a chamber 10. The chamber 10 has therein an inner space 12 c.The chamber 10 includes a chamber body 12. The chamber body 12 has asubstantially cylindrical shape. The chamber body 12 may be formed of,for example, aluminum. A corrosion resistant film is formed on an innerwall surface of the chamber body 12. The corrosion resistant film may bemade of ceramic such as aluminum oxide, yttrium oxide, or the like.

The chamber body 12 has a sidewall having a port 12 p. A substrate W istransferred between the inner space 12 c and the outside of the chamber10 through the port 12 p. The port 12 p is opened and closed by a gatevalve 12 g disposed on the sidewall of the chamber body 12.

A tubular portion 28 is disposed on the bottom of the chamber body 12.The tubular portion 28 may be formed of an insulating material. Thetubular portion 28 has a substantially cylindrical shape. In the innerspace 12 c, the tubular portion 28 extends upward from the bottom of thechamber body 12.

In the inner space 12 c, a support 15 extends upward from the bottom ofthe chamber body 12 along an inner side surface of the substantiallycylindrical tubular portion 28. The support 15 has a substantiallycylindrical shape. The support 15 may be formed of an insulatingmaterial such as ceramic or the like. A substrate support 16 is placedon the support 15. The substrate support 16 is supported by the support15. The substrate support 16 is configured to support the substrate W inthe inner space 12 c.

The substrate support 16 is disposed on the support 15. The substratesupport 16 includes a supporting portion 31, a base 18, and an electrodeplate 21.

The supporting portion 31 includes a substrate supporting portion 31 aon which the substrate W is placed, and a peripheral portion 31 bsurrounding the substrate supporting portion 31 a. A focus ring FRhaving conductivity is placed on the peripheral portion 31 b. Aconductive ring DR is concentrically placed on the cover ring CR toextend along an outer periphery OPc of the focus ring FR. The supportingportion 31 may serve as an electrostatic chuck 20.

The cover ring CR is disposed on the tubular portion 28. The cover ringCR is an insulator and extends along an outer periphery of the substratesupport 16. The cover ring CR is disposed to surround an outer peripheryof the supporting portion 31 when viewed from a position above thesupporting portion 31 (when viewed from an upper electrode 30 side). Thecover ring CR is formed of an insulating material, for example, quartzor ceramic such as alumina or the like. The cover ring CR may include aplurality of dielectric parts.

The conductive ring DR is disposed on the cover ring CR. The conductivering DR is disposed to surround the focus ring FR when viewed from theposition above the supporting portion 31. The conductive ring DR has asubstantially annular plate shape and is formed of a conductivematerial, for example, silicon (Si) or silicon carbide (SiC).

The electrode plate 21 is formed of a conductive material such asaluminum and has a substantially disc shape. The base 18 is disposed onthe electrode plate 21. The base 18 is formed of a conductive materialsuch as aluminum and has a substantially disc shape. The base 18 iselectrically coupled to the electrode plate 21 and functions as a lowerelectrode.

The electrostatic chuck 20 that is the supporting portion 31 is disposedon the base 18. The substrate W is placed on an upper surface of theelectrostatic chuck 20. The electrostatic chuck 20 includes a main bodyand an electrode. The main body of the electrostatic chuck 20 has asubstantially disc shape and is made of a dielectric. The electrode ofthe electrostatic chuck 20 is a film-shaped electrode and is disposed inthe main body of the electrostatic chuck 20. The electrode of theelectrostatic chuck 20 is connected to a direct-current (DC) powersupply (DC) 20 p through a switch 20 s. When a voltage from the DC powersupply 20 p is applied to the electrode of the electrostatic chuck 20,an electrostatic attraction force is generated between the electrostaticchuck 20 and the substrate W. Due to the electrostatic attraction forcethus generated, the substrate W is attracted to and held on theelectrostatic chuck 20.

The focus ring FR is disposed on the peripheral portion 31 b to surroundan outer periphery of the substrate W placed on the substrate supportingportion 31 a. The focus ring FR is provided to improve in-planeuniformity of plasma processing on the substrate W. The focus ring FRhas a substantially annular plate shape and is formed of a conductivematerial, for example, silicon (Si) or silicon carbide (SiC).

A flow channel 18 f is formed in the base 18. A heat exchange medium(e.g., coolant) is supplied from a chiller unit to the flow channel 18 fthrough a line 23 a. The chiller unit is disposed external to thechamber 10. The heat exchange medium supplied to the flow channel 18 freturns to the chiller unit through a line 23 b. In the plasmaprocessing apparatus 1, a temperature of the substrate W placed on theelectrostatic chuck 20 can be adjusted by heat exchange between the heatexchange medium and the base 18.

The plasma processing apparatus 1 may further include a gas supply line25. The gas supply line 25 is provided to supply a heat transfer gas(e.g., He gas) from a heat transfer gas supply mechanism to a spacebetween the upper surface of the electrostatic chuck 20 and a backsurface of the substrate W.

The plasma processing apparatus 1 further includes an upper electrode30. The upper electrode 30 is disposed above the substrate support 16.The upper electrode 30 is supported at an upper portion of the chamberbody 12 through a member 32. The member 32 may be formed of aninsulating material. The upper electrode 30 and the member 32 close atop opening of the chamber body 12.

The upper electrode 30 may include a ceiling plate 34 and a holder 36. Abottom surface of the ceiling plate 34 that faces the inner space 12 cdefines the inner space 12 c. The ceiling plate 34 may be formed of asemiconductor or a low-resistance conductor with low Joule heating. Theceiling plate 34 has multiple gas injection holes 34 a formedtherethrough in a thickness direction of the ceiling plate 34.

The holder 36 detachably holds the ceiling plate 34. The holder 36 maybe formed of a conductive material such as aluminum. A gas diffusionspace 36 a is formed in the holder 36. Multiple gas holes 36 b areformed in the holder 36. The gas holes 36 b extend downward from the gasdiffusion space 36 a. The gas holes 36 b communicate with the gasinjection holes 34 a, respectively. The holder 36 has a gas inlet port36 c. The gas inlet port 36 c is connected to the gas diffusion space 36a. A gas supply line 38 is connected to the gas inlet port 36 c.

The gas supply line 38 is connected to a valve group (VG) 44, a flowrate controller group (FRCG) 42, and a gas source group (GSG) 40. Thegas source group 40, the valve group 44, and the flow rate controllergroup 42 constitute a gas supply unit. The gas source group 40 includesmultiple gas sources. The valve group 44 includes multipleopening/closing valves. The flow rate controller group 42 includesmultiple flow rate controllers. Each of the flow rate controllers of theflow rate controller group 42 is a mass flow controller or a pressurecontrol type flow rate controller. Each of the gas sources of the gassource group is connected to the gas supply line 38 through thecorresponding opening/closing valve of the valve group 44 and thecorresponding flow rate controller of the flow rate controller group 42.

A baffle plate 48 is disposed between the tubular portion 28 and thesidewall of the chamber body 12. The baffle plate 48 is formed bycoating a corrosion resistant film (film made of yttrium oxide or thelike) on a surface of an aluminum base, for example. The baffle plate 48has multiple through-holes. At the bottom portion of the chamber body12, a gas exhaust port is disposed below the baffle plate 48. A gasexhaust unit (GEU) 50 is connected to the gas exhaust port through a gasexhaust line 52. The gas exhaust unit 50 includes a pressure controlvalve and a vacuum pump such as a turbo molecular pump.

The plasma processing apparatus 1 further includes a first radiofrequency (RF) power supply 62 and a second radio frequency (RF) powersupply 64. The first RF power supply 62 is configured to generate afirst RF power. The first RF power has a frequency suitable for plasmageneration. The frequency of the first RF power is within a range of,e.g., 27 MHz to 100 MHz. The first RF power supply 62 is electricallycoupled to the base 18 through a matching unit (MU) 66 and the electrodeplate 21. The matching unit 66 has a matching circuit configured tomatch an output impedance of the first RF power supply 62 and animpedance of a load side (the base 18 side). Alternatively, the first RFpower supply 62 may be electrically coupled to the upper electrode 30through the matching unit 66.

The second RF power supply 64 is configured to generate a second RFpower. The second RF power has a frequency lower than the frequency ofthe first RF power. In the case of using both of the first RF power andthe second RF power, the second RF power is used as a bias RF power forattracting ions to the substrate W. The frequency of the second RF poweris within a range of, e.g., 400 kHz to 13.56 MHz. The second RF powersupply 64 is electrically coupled to the base 18 through a matching unit(MU) 68 and the electrode plate 21. The matching unit 68 has a matchingcircuit configured to match an output impedance of the second RF powersupply 64 and the impedance of the load side (the base 18 side).

The plasma may be generated by using the second RF power alone withoutusing the first RF power. In other words, the plasma may be generated byusing a single RF power. In this case, the frequency of the second RFpower may be higher than 13.56 MHz and may be e.g., 40 MHz. Further, theplasma processing apparatus 1 may not include the first RF power supply62 and the matching unit 66.

In the plasma processing apparatus 1, the plasma is generated bysupplying a gas from the gas supply unit to the inner space 12 c. Bysupplying at least one of the first RF power and the second RF power, RFelectric field is generated between the upper electrode 30 and the base18 (the lower electrode). The plasma is generated by the RF electricfield thus generated.

The plasma processing apparatus 1 may further include a controller MC.The controller MC may be a computer including a processor, a storagedevice such as a memory, an input device, a display device, a signalinput/output interface, and the like. The controller MC is configured tocontrol the individual components of the plasma processing apparatus 1.

The controller MC allows an operator to input commands to manage theplasma processing apparatus 1 through the input device. Further, thecontroller MC allows the display device to visualize and display anoperation status of the plasma processing apparatus 1. Further, acontrol program and recipe data are stored in the storage device. Thecontrol program is executed by the processor to perform variousprocesses in the plasma processing apparatus 1. The processor executesthe control program and controls the individual components of the plasmaprocessing apparatus 1 based on the recipe data.

With reference to FIG. 2, a structure in a region ER of the substratesupport 16 shown in FIG. 1 will be described. Particularly, structuresof the conductive ring DR and the focus ring FR will be described indetail.

In the example shown in FIG. 2, the cover ring CR includes twodielectric members, i.e., an inner cover ring CRa and an outer coverring CRb. The cover ring CR may be formed of one dielectric member ormay include three or more dielectric members.

An inner peripheral side (inner peripheral portion) of the focus ring FRis placed on the electrostatic chuck 20 that is the peripheral portion31 b of the supporting portion 31, and an outer peripheral side (outerperipheral portion) of the focus ring FR is disposed to cover the innercover ring CRa. Alternatively, the outer peripheral portion of the focusring FR may be placed on the inner cover ring CRa. Further, in order tosecurely support the inner peripheral portion of the focus ring FR bythe peripheral portion 31 b, a gap may be formed between a bottomsurface of the outer peripheral portion of the focus ring FR and theupper surface SFa of the inner cover ring CRa by forming an uppersurface SFa of the inner cover ring CRa to be lower than an uppersurface of the peripheral portion 31 b. In other words, the outerperipheral portion of the focus ring FR may not be placed on the innercover ring CRa. A thickness of the main body of the electrostatic chuck20 is very small compared to a thickness of the inner cover ring CRa.Therefore, the focus ring FR is electrically coupled as a RF circuit tothe first RF power supply 62 and the second RF power supply 64 throughthe electrostatic chuck 20. Further, as shown in FIG. 3, a power supplyrod SP that is connected to the DC power supply DC and is in contactwith the bottom surface of the focus ring FR may be disposed in athrough-hole formed through the inner cover ring CRa so that a DCvoltage can be applied to the focus ring FR.

The conductive ring DR is placed on the outer cover ring CRb. Since theouter cover ring CRb has a large thickness, the conductive ring DR isnot electrically coupled as a RF circuit to the first RF power supply 62and the second RF power supply 64 through the outer cover ring CRb.

The outer cover ring CRb has an inner peripheral upper surface SFc andan outer peripheral upper surface SFd. The inner peripheral side of theouter cover ring CRb is closer to the focus ring FR, and thus is moreeasily consumed compared to the outer peripheral side of the outer coverring CRb. Therefore, in the example of FIG. 2, the conductive ring DR isdisposed to cover only a portion that is easily consumed (the innerperipheral upper surface SFc of the outer cover ring CRb). In otherwords, an outer periphery OPd of the conductive ring DR is located onthe inner side compared to an outer periphery OPe of the cover ring CR,and an outer peripheral upper surface SFd of the cover ring CR isexposed to a plasma processing space (the inner space 12 c). However,the conductive ring DR may be disposed to cover the entire upper surfaceof the outer cover ring CRb. Further, in the example of FIG. 2, theouter peripheral upper surface SFd and the inner peripheral uppersurface SFc covered with the conductive ring DR are located on the sameplane. However, they may not be located on the same plane. For example,the height of the upper surface SFd of the outer cover ring CRb that isnot covered with the conductive ring DR may be higher than or equal tothe height of an upper surface SFb of the conductive ring DR.

As shown in FIG. 2, a gap AS is formed between the focus ring FR and theconductive ring DR. More specifically, a first side surface SSa on theouter periphery OPc of the focus ring FR and a second side surface SSbon an inner periphery IPb of the conductive ring DR are spaced apartfrom each other while facing each other. An inner peripheral bottomsurface ILSb of the conductive ring DR is disposed below an outerperipheral bottom surface ILSa of the focus ring FR.

In the example shown in FIG. 2, an area of the second side surface SSbis smaller than an area of the upper surface SFb of the conductive ringDR. The upper surface SFb of the conductive ring DR is higher than theupper surface of the focus ring FR. In other words, a thickness of theinner periphery IPb of the conductive ring DR is greater than athickness of the outer periphery OPc of the focus ring FR.

A distance GA between the first side surface SSa and the second sidesurface SSb is a width of the gap AS. As will be described later, thefirst side surface SSa and the second side surface SSb function as acapacitor. Therefore, the distance GA is preferably greater than zeroand smaller than a thickness SH of the focus ring FR.

The cover ring CR further includes a spacing portion DT. The spacingportion DT separates the first side surface SSa of the focus ring FRfrom the second side surface SSb of the conductive ring DR.

In the example shown in FIG. 2, the inner peripheral upper surface SFcof the outer cover ring CRb is lower than the inner peripheral uppersurface SFa of the inner cover ring CRa, so that the spacing portion DTthat is a stepped portion is formed between the inner cover ring CRa andthe outer cover ring CRb. Since the stepped portion is in contact withthe second side surface SSb of the conductive ring DR, the second sidesurface SSb of the conductive ring DR is not in contact with the firstside surface SSa of the focus ring FR. In other words, due to thespacing portion DT, it is possible to prevent the first side surface SSaand the second side surface SSb from being in contact with each other soas not to function as the capacitor.

In the substrate support 16 configured as described above, theconductive ring DR is disposed on the cover ring CR. Further, since thethickness of the cover ring CR is greater than the thickness of the mainbody of the electrostatic chuck 20, the conductive ring DR is notelectrically coupled as a RF circuit to the first RF power supply 62 andthe second RF power supply 64 through the cover ring CR. Further, thefirst side surface SSa of the outer periphery OPc of the focus ring FRand the second side surface SSb of the inner periphery IPb of theconductive ring DR are spaced apart from each other while facing eachother. Therefore, the first side surface SSa and the second side surfaceSSb function as the capacitor. In other words, the focus ring FR and theconductive ring DR are capacitively coupled between the first sidesurface SSa and the second side surface SSb. When the RF power isapplied to the base 18, positive or negative charges existing on thefirst side surface SSa of the outer periphery OPc of the focus ring FRcause electrostatic induction in the conductive ring DR. Accordingly,charges whose amount is the same as that of charges collected on thesecond side surface SSb of the conductive ring DR and whose polarity isopposite to that of the charges collected on the second side surface SSbof the conductive ring DR are attracted by the potential of the plasmaand collected on the upper surface SFb of the conductive ring DR. Sincethe area of the upper surface SFb is greater than the area of the secondside surface SSb, the amount of charges per unit area on the uppersurface SFb is smaller than that on the second side surface SSb.Therefore, the potential of the conductive ring DR becomes lower thanthe potential of the focus ring FR, and acceleration of ions in theplasma toward the conductive ring DR is suppressed. Accordingly, theconductive ring DR (i.e., the outer region of the focus ring FR) is lesslikely to be sputtered.

The conductive ring DR is disposed to cover a portion of the cover ringCR that is easily consumed and is made of a material having higherresistance to the sputtering compared to the resistance of the coverring CR. Further, since the acceleration of ions toward the conductivering DR is suppressed, the conductive ring DR itself is also less likelyto be sputtered. Therefore, it is possible to suppress the areavariation of the focus ring FR serving as the cathode due to theconsumption of the cover ring CR near the outer periphery of the focusring FR. Accordingly, it is possible to suppress process variation suchas occurrence of tilting at the edge of the substrate and the like.

Further, by adjusting the area of the upper surface SFb of theconductive ring DR, the potential of the upper surface SFb of theconductive ring DR can be adjusted.

In addition, the conductive ring DR is disposed to face the first sidesurface SSa of the focus ring FR. Since an object (conductive ring DR)is disposed at the side of the first side surface SSa of the focus ringFR, ions moving toward the first side surface SSa are blocked by theconductive ring DR. Therefore, the focus ring FR is less likely to besputtered from the first side surface SSa, which makes it possible tosuppress the consumption of the focus ring FR.

In the example shown in FIG. 2, the substrate supporting portion 31 aand the peripheral portion 31 b on which the focus ring FR is placedserve as the electrostatic chuck 20. However, the present disclosure isnot limited thereto. An electrostatic chuck that is the substratesupporting portion 31 a and an electrostatic chuck that is theperipheral portion 31 b may be separately provided. Alternatively, asshown in FIG. 4, only the substrate supporting portion 31 a may beconfigured as the electrostatic chuck 20, and the peripheral portion 31b may be configured as the base 18. Further, the entire focus ringincluding the inner peripheral side of the focus ring FR may be placedon the peripheral portion 31 b. The peripheral portion 31 b may beformed lower than the substrate supporting portion 31 a so that astepped portion can be formed.

Further, in the example shown in FIG. 2, the inner peripheral uppersurface SFc of the outer cover ring CRb is lower than the upper surfaceSFa of the inner cover ring CRa, so that the spacing portion DT isformed. However, the present disclosure is not limited thereto. As shownin FIG. 5, a concave groove may be formed at a portion of the cover ringCR on which the conductive ring DR is placed, and an inner peripheralbottom surface ILSb of the conductive ring DR may extend downwardly(convex shape). In this case, the inner peripheral bottom surface ILSbof the conductive ring DR is fitted in the groove of the cover ring CR.By fitting the convex inner peripheral bottom surface ILSb into theconcave groove, the position of the conductive ring DR in the cover ringCR can be stably maintained. Although the groove is formed as thespacing portion DT at the outer cover ring CRb in FIG. 5, the groove maybe formed at the inner cover ring CRa. In this case, the innerperipheral portion of the conductive ring DR is placed on the innercover ring CRa, and the outer peripheral portion of the conductive ringDR is placed on the outer cover ring CRb. In FIG. 5, the upper surfaceSFa of the cover ring CR on which the focus ring FR is placed and theupper surface SFc of the cover ring CR on which the conductive ring DRis placed have the same height. However, the upper surface SFa and theupper surface SFC may have different heights. For example, the uppersurface SFc of the cover ring CR on which the conductive ring DR isplaced may be higher than the upper surface SFa of the cover ring CR onwhich the focus ring FR is placed.

Further, in the example shown in FIG. 2, the first side surface SSa ofthe focus ring FR and the second side surface SSb of the conductive ringDR are spaced apart from each other while facing each other to functionas the capacitor. However, the present disclosure is not limitedthereto. As shown in FIG. 6, an outer peripheral bottom surface of thefocus ring FR and an inner peripheral upper surface of the conductivering DR may be spaced apart from each other while facing each other. InFIG. 6, a lower inner peripheral portion of the conductive ring DRprotrudes toward the inner peripheral side. The upper surface of theprotruding lower inner peripheral portion of the conductive ring DR andthe bottom surface of the focus ring FR are spaced apart from each otherwhile facing each other. Further, the first side surface SSa of thefocus ring FR and the second side surface SSb that is a side surface ofan upper inner peripheral portion of the conductive ring DR are spacedapart from each other while facing each other.

The inner peripheral upper surface SFc of the outer cover ring CRb islower than the upper surface SFa of the inner cover ring CRa, and thespacing portion DT that is a stepped portion is formed between the innercover ring CRa and the outer cover ring CRb. Since a third side surfaceSSc that is a side surface of the lower inner peripheral portion of theconductive ring DR is in contact with the stepped portion (the outerperipheral side surface of the inner cover ring CRa), the second sidesurface SSb that is the side surface of the upper inner peripheralportion of the conductive ring DR is not in contact with the first sidesurface SSa of the focus ring FR. The upper surface SFa of the innercover ring CRa is higher than the upper surface of the lower innerperipheral portion of the conductive ring DR. Therefore, the bottomsurface of the focus ring FR is in contact with the upper surface SFa ofthe inner cover ring CRa, and the upper surface of the lower innerperipheral portion of the conductive ring DR is not in contact with thebottom surface of the focus ring.

In the example shown in FIG. 6, not only the first side surface SSa andthe second side surface SSb but also the outer peripheral bottom surfaceof the focus ring FR and the upper surface of the lower inner peripheralportion of the conductive ring DR can function as the capacitor.Accordingly, the capacitance between the focus ring FR and theconductive ring DR can be increased.

A distance GB between the outer peripheral bottom surface of the focusring FR and the upper surface of the lower inner peripheral portion ofthe conductive ring DR may be smaller than the distance GA between thefirst side surface SSa and the second side surface SSb. Since thedistance GB is smaller than the distance GA, the capacitance between theouter peripheral bottom surface of the focus ring FR and the uppersurface of the lower inner peripheral portion of the conductive ring DRbecomes greater than the capacitance between the first side surface SSaand the second side surface SSb. Therefore, even if the areas of thefirst side surface SSa and the second side surface SSb are changed dueto the consumption of the focus ring FR and the conductive ring DR, thecapacitance variation between the focus ring FR and the conductive ringDR can be reduced. Further, since the distance GA between the first sidesurface SSa and the second side surface SSb can be increased, it ispossible to prevent the gap AS from being closed (filled) by depositsand becoming unable to function as the capacitor or having largevariation in capacitance.

An area of the upper surface of the lower inner peripheral portion ofthe conductive ring DR facing the outer peripheral bottom surface of thefocus ring FR may be greater than an area of the inner peripheral sidesurface of the conductive ring DR facing the outer peripheral sidesurface of the focus ring FR. In this case, since the capacitancebetween the outer peripheral bottom surface of the focus ring FR and theupper surface of the lower inner peripheral portion of the conductivering DR increases, the capacitance variation between the focus ring FRand the conductive ring DR can be reduced.

Further, as illustrated in the example shown in FIG. 6, a sloped portionmay be formed between the inner peripheral side surface and the uppersurface of the conductive ring DR. Due to the sloped portion, thechanges in height between the upper surface of the focus ring FR and theupper surface of the conductive ring DR can be smooth, and discontinuityin the sheath formed above the conductive ring DR and the focus ring FRcan be decreased.

In the examples shown in FIGS. 2 to 6, the upper surface SFb of theconductive ring DR is higher than the upper surface of the focus ringFR. However, the present disclosure is not limited thereto. The heightof the upper surface SFb of the conductive ring DR may be lower than orequal to that of the upper surface of the focus ring FR.

In the example shown in FIG. 6, the outer peripheral bottom surface ofthe focus ring FR and the inner peripheral upper surface of theconductive ring DR are spaced apart from each other while facing eachother. Alternatively, as shown in FIG. 7, an outer peripheral uppersurface of the focus ring FR and an inner peripheral bottom surface ofthe conductive ring DR may be spaced apart from each other while facingeach other.

In the conductive ring DR shown in FIG. 7, an upper inner peripheralportion of the conductive ring DR protrudes toward the inner peripheralside. The bottom surface of the protruding upper inner peripheralportion of the conductive ring DR and the upper surface of the focusring FR are spaced apart from each other while facing each other.Further, the first side surface SSa of the focus ring FR and the secondside surface SSb that is a side surface of a lower inner peripheralportion of the conductive ring DR are spaced apart from each other whilefacing each other.

The inner peripheral upper surface SFc of the outer cover ring CRb islower than the upper surface SFa of the inner cover ring CRa, so thatthe spacing portion DT that is a stepped portion is formed between theinner cover ring CRa and the outer cover ring CRb. Since a portion ofthe second side surface SSb that is the side surface of the lower innerperipheral portion of the conductive ring DR is in contact with thestepped portion (the outer peripheral side surface of the inner coverring CRa), a portion of the second side surface SSb that is the sidesurface of the upper inner peripheral portion of the conductive ring DRis not in contact with the first side surface SSa of the focus ring FR.The bottom surface of the protruding upper inner peripheral portion ofthe conductive ring CRa is higher than the outer peripheral uppersurface of the focus ring FR. Therefore, the bottom surface of the upperinner peripheral portion of the conductive ring DR is not in contactwith the upper surface of the focus ring FR.

Similar to the example shown in FIG. 6, a distance GC between the outerperipheral upper surface of the focus ring FR and the bottom surface ofthe upper inner peripheral portion of the conductive ring DR may besmaller than the distance GA between the first side surface SSa and thesecond side surface SSb. An area of the bottom surface of the upperinner peripheral portion of the conductive ring DR facing the outerperipheral upper surface of the focus ring FR may be greater than anarea of the inner peripheral side surface of the conductive ring DRfacing the outer peripheral side surface of the focus ring FR.

In the example shown in FIG. 7, the gap AS is covered by the upper innerperipheral portion of the conductive ring DR, so that it is possible toprevent the gap AS from being closed (filled) by deposits and becomingunable to function as a capacitor or having large variation incapacitance.

In the examples shown in FIGS. 6 and 7, the outer peripheral bottomsurface (upper surface) of the focus ring FR and the inner peripheralupper surface (bottom surface) of the conductive ring DR are spacedapart from each other while facing each other, and the first sidesurface SSa of the focus ring FR and the second side surface SSb of theconductive ring DR are spaced apart from each other while facing eachother. However, only the outer peripheral bottom surface (upper surface)of the focus ring FR and the inner peripheral upper surface (bottomsurface) of the conductive ring DR may be spaced apart from each otherwhile facing each other.

In the examples shown in FIGS. 2 to 7, the focus ring FR is disposed tocover the inner cover ring CRa on the outer peripheral side (outerperipheral portion) of the focus ring FR. However, the entire focus ringFR may be disposed on the electrostatic chuck 20 or on the base 18. Inother words, not only the inner peripheral side (inner peripheralportion) of the focus ring FR but also the outer peripheral side (outerperipheral portion) of the focus ring FR may be placed on the base 18 orthe electrostatic chuck that is the peripheral portion 31 b of thesupporting portion 31.

FIG. 8 shows an example in which only the outer peripheral upper surfaceof the focus ring FR and the inner peripheral bottom surface of theconductive ring DR are spaced apart from each other while facing eachother. Further, the entire focus ring FR is placed on the electrostaticchuck 20.

The inner peripheral portion of the cover ring CR is placed on the outerperipheral portion of the focus ring FR. The conductive ring DR isplaced on the cover ring CR. The inner peripheral portion of theconductive ring DR has a downwardly protruding portion. A bottom surfaceof the protruding portion (inner peripheral bottom surface) of theconductive ring DR and the outer peripheral upper surface of the focusring FR are spaced apart from each other while facing each other. Sincethe conductive ring DR is placed on the cover ring CR, the upper surfaceof the cover ring CR and the outer peripheral bottom surface of theconductive ring DR are in contact with each other. In other words, theupper surface of the cover ring CR serves as the spacing portion DT, andthe bottom surface of the protruding portion of the conductive ring DRand the outer peripheral upper surface of the focus ring FR are not incontact with each other. Although the downwardly protruding portion isformed at the inner peripheral portion of the conductive ring DR in theexample shown in FIG. 8, the protruding portion may not be formed aslong as a sufficient capacitance can be obtained between the innerperipheral bottom surface of the conductive ring DR and the outerperipheral upper surface of the focus ring.

While various embodiments have been described above, various omissions,substitutions, and changes may be made without being limited to theabove-described embodiments. Further, other embodiments can beimplemented by combining elements in different embodiments.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosures. Indeed, the embodiments described herein maybe embodied in a variety of other forms. Furthermore, various omissions,substitutions and changes in the form of the embodiments describedherein may be made departing from the spirit of the disclosures. Theaccompanying claims and their equivalents are intended to cover suchforms or modifications as would fall within the scope and spirit of thedisclosures.

The invention claimed is:
 1. A plasma processing apparatus comprising: asubstrate support having a substrate supporting portion on which asubstrate is placed and a peripheral portion surrounding the substratesupporting portion; a conductive focus ring placed on the peripheralportion of the substrate support; a cover ring surrounding an outerperiphery of the substrate support and formed of a dielectric material;a conductive ring placed on the cover ring; and a radio frequency powersupply electrically coupled to the substrate support, wherein a firstsurface on an outer peripheral portion of the focus ring and a secondsurface on an inner peripheral portion of the conductive ring are spacedapart from each other while facing each other, and the cover ring has aspacing portion that separates the focus ring from the conductive ring.2. The plasma processing apparatus of claim 1, wherein an innerperipheral portion of the focus ring is supported on the peripheralportion of the substrate support, and the outer peripheral portion ofthe focus ring covers an upper surface of an inner peripheral portion ofthe cover ring.
 3. The plasma processing apparatus of claim 1, whereinthe first surface is a side surface of the outer peripheral portion ofthe focus ring, and the second surface is a side surface of the innerperipheral portion of the conductive ring.
 4. The plasma processingapparatus of claim 1, wherein the first surface is a bottom surface ofthe outer peripheral portion of the focus ring, and the second surfaceis an upper surface of the inner peripheral portion of the conductivering.
 5. The plasma processing apparatus of claim 1, wherein the firstsurface is an upper surface of the outer peripheral portion of the focusring, and the second surface is a bottom surface of the inner peripheralportion of the conductive ring.
 6. The plasma processing apparatus ofclaim 4, wherein a side surface of the outer peripheral portion of thefocus ring and a side surface of the inner peripheral portion of theconductive ring are spaced apart from each other while facing eachother.
 7. The plasma processing apparatus of claim 6, wherein an area ofthe upper surface of the inner peripheral portion of the conductive ringfacing the bottom surface of the outer peripheral portion of the focusring is greater than an area of the side surface of the inner peripheralportion of the conductive ring facing the side surface of the outerperipheral portion of the focus ring.
 8. The plasma processing apparatusof claim 6, wherein a gap between the bottom surface of the outerperipheral portion of the focus ring and the upper surface of the innerperipheral portion of the conductive ring is smaller than a gap betweenthe side surface of the outer peripheral portion of the focus ring andthe side surface of the inner peripheral portion of the conductive ring.9. The plasma processing apparatus of claim 1, wherein the focus ringand the conductive ring are capacitively coupled between the firstsurface and the second surface.
 10. The plasma processing apparatus ofclaim 1, wherein a distance between the first surface and the secondsurface is greater than zero and smaller than a thickness of the focusring.
 11. The plasma processing apparatus of claim 1, wherein a bottomsurface of the inner peripheral portion of the conductive ring is lowerthan a bottom surface of the outer peripheral portion of the focus ring.12. The plasma processing apparatus of claim 1, wherein the spacingportion is a groove portion formed on a surface of the cover ring, and abottom surface of the inner peripheral portion of the conductive ring isfitted in the groove portion.
 13. The plasma processing apparatus ofclaim 1, wherein the spacing portion is a stepped portion formed on asurface of the cover ring that is in contact with a side surface of theinner peripheral portion of the conductive ring.
 14. The plasmaprocessing apparatus of claim 1, wherein the conductive ring is disposedon the cover ring such that an outer periphery of the conductive ring islocated on an inner side compared to an outer periphery of the coverring, and an upper surface of an outer peripheral portion of the coverring is exposed to a plasma processing space.
 15. The plasma processingapparatus of claim 1, wherein the cover ring includes a plurality ofdielectric parts.
 16. The plasma processing apparatus of claim 1,wherein the substrate supporting portion and the peripheral portionserve as an electrostatic chuck.
 17. The plasma processing apparatus ofclaim 1, wherein the substrate supporting portion serves as anelectrostatic chuck, and the peripheral portion serves as a base of thesubstrate support.
 18. The plasma processing apparatus of claim 1,wherein the conductive ring has a sloped portion between an uppersurface of the conductive ring and a side surface of the innerperipheral portion of the conductive ring.
 19. The plasma processingapparatus of claim 1, wherein the conductive ring is formed of siliconor silicon carbide, and the cover ring is formed of quartz.